Bug 17678: C4::Circulation - Replace GetIssues with Koha::Issues

Bug 17678: C4::Circulation - Replace GetIssues with Koha::Issues

The C4::Circulation::GetIssues subroutine is only called once and can be
replaced with a call to Koha::Isues->search with a join on items.

Test plan:
- Apply first patch and make sure the tests pass
- Apply second patch and make sure the tests still pass

Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>